At the smallest scales of distance and duration that we can measure, space-time - that is, the three dimensions of space plus time - appears to be smooth and structureless. Think of flying over the ocean in an airplane. From 30,000 feet or so, the ocean appears completely smooth. However, if your plane were to descend low enough, you could make out the waves and swells of the water. Certain aspects of quantum mechanics, the highly successful theory scientists have developed to explain the physics of atoms and subatomic particles, predict that space-time may act the same way. Instead of being totally smooth, it would have a foamy, jittery nature if we could look at small enough scales -- like those waves on the ocean. In these models, space-time would consist of many small, ever-changing, regions for which space and time are constantly fluctuating.

Since space-time foam, as it is called, is so tiny, scientists cannot observe it directly. However, they can hunt for evidence for its existence - or non-existence - in things we can see. By looking at the light from distant quasars in X-rays from Chandra as well as gamma-ray telescopes, a team of scientists set out to test some of the models of space-time foam.

What did they find? The researchers say their evidence can help rule out two different models of space-time foam. While their work does not eliminate the existence of space-time foam entirely, it does suggest that space-time is less foamy than some models predict. Scientists will continue to test the nature of space and time on the very smallest scales using every experiment they can think of, including using high-energy light from across the Universe.
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A group of unusual giant black holes may be consuming excessive amounts of matter, according to a new study using NASA's Chandra X-ray Observatory. This finding may help astronomers understand how the largest black holes were able to grow so rapidly in the early Universe.

Astronomers have known for some time that supermassive black holes - with masses ranging from millions to billions of times the mass of the Sun and residing at the centers of galaxies - can gobble up huge quantities of gas and dust that have fallen into their gravitational pull. As the matter falls towards these black holes, it glows with such brilliance that they can be seen billions of light years away. Astronomers call these extremely ravenous black holes "quasars."

This new result suggests that some quasars are even more adept at devouring material than previously thought, about five to ten times the rate of typical quasars. A team of astronomers examined data from Chandra for 51 quasars that are located at a distance between about 5 billion and 11.5 billion light years from Earth. Based on their findings, the researchers think some of these quasars contain black holes that are surrounded by a thick, donut-shaped disk of material. This torus would block much of the light - including X-rays and ultraviolet light -- that would otherwise be observed by Chandra and other telescopes. The important implication for these thick-disk quasars is that they may be harboring black holes that are growing an extraordinarily rapid rate.
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Have you ever played with magnets? You might have done an experiment where you lay a magnet onto a table and place an iron nail nearby. If you push the magnet slowly toward the nail, there will come a point when the nail jumps across and sticks to the magnet. That's because magnets have something invisible that extends all around them, called a 'magnetic field'. It can cause a pushing or pulling force on other objects, even if the magnet isn't actually touching them.

The most powerful magnets in the Universe are called magnetars. These are tiny, super-compact stars, 50 times more massive than our Sun, squashed into a ball just 20 kilometers across. (That's about the size of a small city!)

Astronomers think magnetars may be created when some massive stars die in a supernova explosion. The star's gases blow out into space creating a colourful cloud like the one in this picture, called Kes 73. At the same time, the core of the star squashes down to form a magnetar.

At the center of the cosmic cloud in this photograph lies a tiny magnetar. But what this star lacks in size it makes up for in energy, shooting out powerful jets of X-rays every few seconds! You can see the X-ray jets in blue in this photograph.
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The year of 2015 has been declared the International Year of Light, or IYL for short, by the United Nations. Organizations, institutions, and individuals involved in the science and applications of light will be joining together for this year-long celebration to help spread the word about the wonders of light.

In many ways, astronomy uses the science of light. By building telescopes that can detect light in its many forms from radio waves on one end of the "electromagnetic spectrum" to gamma rays on the other, scientists can get a better understanding of the processes at work in the Universe.

NASA's Chandra X-ray Observatory explores the Universe in X-rays, a high-energy form of light. By studying X-ray data and comparing them with observations in other types of light, scientists can develop a better understanding of objects that generate temperatures of millions of degrees and produce X-rays.

To recognize the start of IYL, the Chandra X-ray Center is releasing a collection of images that combine data from telescopes tuned to different wavelengths of light. From a distant galaxy to the relatively nearby debris field of an exploded star, these images demonstrate the myriad ways that information about the Universe is communicated to us through light.

So join us in celebrating IYL and all of the amazing things that light can do, including how it helps us understand the Universe we live in.
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Every year, NASA's Chandra X-ray Observatory looks at hundreds of objects throughout space to help expand our understanding of the Universe. Ultimately, these data are stored in the Chandra Data Archive, an electronic repository that provides access to these unique X-ray findings for anyone who would like to explore them. With the passing of Chandra's 15th anniversary, in operation since August 26, 1999, the archive continues to grow as each successive year adds to the enormous and invaluable dataset.

To celebrate Chandra's decade and a half in space, and to honor October as American Archive Month, a variety of objects have been selected from Chandra's archive. Each of the new images we have produced combines Chandra data with those from other telescopes. This technique of creating "multiwavelength" images allows scientists and the public to see how X-rays fit with data of other types of light, such as optical, radio, and infrared. As scientists continue to make new discoveries with the telescope, the burgeoning archive will allow us to see the high-energy Universe as only Chandra can.
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NGC 4258, also known as Messier 106, is a spiral galaxy like the Milky Way. This galaxy is famous, however, for something that our Galaxy doesn’t have – two extra spiral arms that glow in X-ray, optical, and radio light. These features, or anomalous arms, are not aligned with the plane of the galaxy, but instead intersect with it. The X-ray image from Chandra reveals huge bubbles of hot gas above and below the plane of the galaxy. These bubbles indicate that much of the gas that was originally in the disk of the galaxy has been heated to millions of degrees and ejected into the outer regions by the jets from the black hole. The ejection of gas from the disk by the jets has important implications for the fate of this galaxy. Researchers estimate that all of the remaining gas will be ejected within the next 300 million years -- very soon on cosmic time scales – unless it is somehow replenished. Without this gas, relatively few stars can form there. In fact, scientists estimate that that star formation in the central region of NGC 4258 is already being choked off, with stars forming at a rate ten times less than in the Milky Way galaxy.
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Black holes seem like such mysterious and complicated objects. On one hand, they are, and astronomers have been studying them for decades to learn more. On the other, black holes are actually quite simple. By this, we mean that black holes are defined by just two simple characteristics: their mass and their spin. While astronomers have long been able to measure black hole masses very effectively, determining their spins has been much more difficult. A new result from researchers using data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton takes a step in addressing the spin question. By a lucky alignment, the light from a quasar some 6 billion light years has been magnified and amplified due to an effect called gravitational lensing. This allowed researchers to get detailed information about the amount of X-rays seen at different energies. This, in turn, gave the researchers information about how fast the supermassive black hole at the center of the quasar is spinning. When combined with the spins from other black holes using more indirect methods, astronomers are beginning to better understand just how black holes grow over time across the Universe.
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Just weeks after NASA's Chandra X-ray Observatory began operations in 1999, the telescope pointed at Centaurus A (Cen A, for short). This galaxy, at a distance of about 12 million light years from Earth, contains a gargantuan jet blasting away from a central supermassive black hole.

Since then, Chandra has returned its attention to this galaxy, each time gathering more data. And, like an old family photo that has been digitally restored, new processing techniques are providing astronomers with a new look at this old galactic friend.

This new image of Cen A contains data from observations, equivalent to over nine and a half days worth of observing time, taken between 1999 and 2012. In this image, the lowest-energy X-rays Chandra detects are in red, while the medium-energy X-rays are green, and the highest-energy ones are blue.

As in all of Chandra's images of Cen A, this one shows the spectacular jet of outflowing material that is generated by the giant black hole at the galaxy's center. The new image also highlights a dust lane that wraps around the waist of the galaxy. Astronomers think this feature is a remnant of a collision that Cen A experienced with a smaller galaxy millions of years ago.

In addition to allowing for the creation of new images, the data housed in Chandra's extensive archive on Cen A provide a rich resource for a wide range of scientific investigations. For example, just last year researchers published new findings on the point-like X-ray sources in Cen A. They found that these sources had masses that fell into two categories. These separate groups correspond to systems where either a neutron star or a black hole is pulling material from a companion star. Information like this may tell us important details about the way the massive stars explode, and gives us even more reason to appreciate this new view of a familiar object.
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Pictures of space are often gorgeous. But one of the most exciting things about them is that, very often, they show us things that are invisible to the human eye. This picture in particular does that. In the middle of the photograph lurks an invisible monster, called a super-massive black hole To make this invisible object even harder to study, it is hidden under a thick cloud of dust at the centre of its home galaxy! Even the bright blobs of colour you can see are patches of light that our eyes cannot detect naturally. The pink colour shows radio light, and X-rays are shown in blue.

A black hole is anything but empty space, don't let the name fool you. It is a huge amount of material packed into a very tiny area - this one has about 100 million times the mass of our Sun! Anything that wanders too close to a Black Hole is pulled into it with no chance of escape, including light. This is why we cannot see black holes, they are invisible even to telescopes that detect X-rays, radio waves and other types of light.

The only way we can spot black holes is by detecting its effect on other things. For example, in this picture, the brightest blue patches, along the edge of the galaxy reveal where a high-energy jet has ploughed into clumps of galactic dust. The jet was made up of particles that were heated as they were pulled into the black hole. This gave them energy and sent them speeding away from the black hole at millions of miles per hour! Two similar jets can be seen in pink, shooting to the North and South of the galaxy.

Astronomers think that just about every galaxy contains a giant, or supermassive, black hole at their center. Sometimes the intense gravity of these black holes can be tapped to produce intense power. That's what is happening in the galaxy known as 4C+29.30, which is found some 850 million light years from Earth. By looking at this galaxy with different telescopes, astronomers can get a more complete picture. Radio data show two jets of particles that are speeding at millions of miles per hour away from the supermassive black hole. X-rays from Chandra trace the location of hot gas in the galaxy. The bright X-rays in the center of the image mark a pool of million-degree gas around the black hole. Some of this material may eventually be consumed by the black hole, and the magnetized, whirlpool of gas near the black hole could, in turn, trigger more output to the radio jet. Most of the low-energy X-rays around the black hole are absorbed by dust and gas, which is probably in the shape of a giant doughnut around the black hole. This doughnut, or torus, blocks all the optical light produced near the black hole, so astronomers refer to this type of source as a hidden or buried black hole.
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